Surge-protected circuit interrupter



Aug. 22, 1939. R. R. PITTMAN Er AL 2,170,337 l SERGE-PROTECTED CIRCUIT INTERRUlTER Filed March 31, 1939 To LOAD TO SOURC E INVENTORS @y WP' Patented Aug. 22, 1939 UNITED STATES SURGE-PROTECTED CIRCUIT INTERRUPTER Ralph R. Pittman and Carroll H. Walsh, Pine Bluff, Ark.

Application March 31, 1939, Serial No. 265,066

12 Claims.

ing the passage of overcurrents through the` switching device; the provision of means for selecting the terminal from which a discharge will occur; and means for providing a structure embodying the switching device in which the excessvoltage device and connecting members frm a part` of the supporting structure. Other objects will be in part-obvious, andin part pointed out hereinafter.

The invention comprises the elements and combinations thereof, features of construction, and arrangement'l of parts to be exemplified in the description to follow, and the scope of the invention will be indicated in the .accompanying claims.

The single figure of the drawing illustrates as a side elevational view, shown partly in section, an embodiment of our invention.

It has long been recognized that some sort of excess-voltage responsive and arc-extinguishing device, sometimes referred to as alightning arrester, is`a desirable device for installation at each end of an overcurrent-responsive sectionalizing switch, in order'that the energy superimposed on the connected conductors as a result of lightning discharges may be directed to ground over a preferential path on each side of the switch; first, to prevent the energy from passing through the switch in its passage from conductor to ground; and second, to provide the necessary protection in case the switch is open-circuited, as in the case of a blown fuse. Heretofore it has been common practice to -employ two voltage-responsive devices or lightning arresters, positioned at the respective ends of the switch. Our invention herein provides an arrangement in which only one voltage-responsive device is required, but at the same time provides the desired protection for both the line and load ends or terminals of the switching device.

The manner in which our invention meets the foregoing protective requirements while embodylng only a single excess-voltage device will be clear from the following description.

Referring to the drawing, a horizontally positioned metal base I2 is secured intermediate its ends to the wood support I0 by means of the U- 5 bolt II. A pair of Serial joined insulators 24 and 25 extend downwardly from one end of the Y base I2, and a conducting load terminal 4I is secured in any suitable manner at the lower end -of the lower insulator 25. At the other end of l0 the base I2, an excess-voltage responsive device 45, to be described more in detail, is secured, extending downwardly in parallel relationship with the insulators 24 and 25, and an insulator 26 is rigidly secured to the lower end of the excess- 15 voltage' device 45, the insulator 26 extending co- `axially downward and having secured thereto at its -lower end the conducting terminal 30, the arrangement being such that the lower ends of the insulators 25 and 26 are at substantially the 20 same elevation.

'Ihe excess-voltage device 45 illustrated herein Vis similar in some respects in construction to the structure shown in Patent No. 2,065,152, dated Dec. 22, 1936, and issued to Ralph R. Pittman, 25 and includes the ground terminal I5 at the upper end thereof, which is electrically connected to the ground I3 through the ground conductor I4. In general the excess-voltage means 45 comprises a tubular insulator I8, preferable of ceramic 30 material, within which is disposed an assembly including the tubular element I9, which in turn contains thex cylindrical filler 20, the latter elements being preferably constructed from hard fiber. A portionof the conducting terminal II 35 extends into the tubular insulator I9, and the upper end of the latter is closed 'by means of the threaded metal plug 22. To assure breakdown within the 'tubular insulator I9, a conducting electrode 2| extends upwardly from the lower ter- 40 mlnal II toward the grounded metal plug 22, this establishing the weakest electrical path through `the device, the spacing between the up per end of the electrode 2l and the plug 22 determining the voltage at which the device breaks 45 down to eiect current flow therethrough. An opening 46 at the lower terminal I'I communicates Withthe interior of the tubular insulator I9, for the purpose of venting the arc products to the atmosphere. It4 may be noted that any other de- 5C vice embodying a structure which breaks down at a predetermined voltage to effect ilow of 'cur-` rent therethrough and means for extinguishing the arc so initiated may be used in the organization of the present invention. 55

The excess-voltage device is embraced intermediate its ends by the clamp I6, which extends around the ceramic housing |8, and is rigidly attached to the base 2 by means of the bolt 41.

An4 electrode of conducting material 23 is rigidly secured at one end between the conducting terminal |1 of the excess-voltage means 45, and the upper end of the insulator 26., and extends horizontally, in spaced parallel relation with the base l2, to the juncture of the. lower end of the upper insulator 24 with the upper end of the lower insulator 25, being rigidlyclamped between the' members abovementioned at its respective ends.

At the lower end of the insulators 25 and 26, a fuse tube 34, having the contacts 33 and 39 at its respective ends electrically connected through the fusible element 36 of the fuse link 35, the latter extending through the fuse tube, is removably supported in a substantially horizontal position through frictional engagement of the contacts 33 and 39 with the terminal clips 30 and 4| respectively. To assist in guiding the'fuse tube, a pair of hooks 43 provide a seat in which the pintles 44 may rotate as the tube is swung from the closed position shown by the full lines to the open position indicated by the dashed lines.

At the line or source end of the interrupter, a line Wire connector 29 electrically connects the line conductor 21 to the line terminal 30, and in a similar manner, at the load end a load wire connector 42 connects the load wire 28 to the terminal 4|.

'An electrode 3|, electrically connected to the line terminal 30, extends rst laterally therefrom, and then upwardly along but spaced from the insulator 26, in spaced relationship with the conducting member or electrode 23, to form the spark gap indicated at 31. At the load end of the device, a conducting electrode 32, mechanically joined to the contact 39 by means of the screws 40, and electrically connected to the load terminal 4|, extends in a similar manner upwardly along and spaced from the insulator 25, in spaced relationship with the conducting member or electrode 23v to form the spark gap indicated at 38.

From the above description, it will be apparent that the ground terminal l5 of the excess-voltage means 45 is maintained at ground potential through the conductor I4; that the ungrounded conducting terminal |1 of the excess-voltage means 45 and the electrode 23, being physically in contact, are maintained at the same potential; also that the electrodes 3| and 32, when electrically connected under normal conditions by thev fuse link 35, are at the same potential with respect to eachother, but ata different potential with respect to the electrode or conducting member 23. Further, when the fusible element of the fused link is fused, the potential of the electrodes 3| and 32 may diier both with lrespect to each other and with respect to the The important considerations are: (1) 'I'he electrical strength of the insulator 26 should be greater than that of the spark gap 31; the electrical strength of the insulator 25 should be greater than that of the spark gap 38; the electrical strength of any path from the electrode 23 to the ground terminal l5 should be greater than that of the excess-voltage device 45. Assuming these conditions to be met, it will be apparent that an abnormal voltage ofl suicient magnitude to cause ow of current from either of the terminals 30 or 4| to ground will cause such current to flow through the excess-voltage device 45. This being true, it becomes clear that only one excess-voltage means is required to provide the desired protection for all of the insulating members of the switching structure, regardless of whether the fuse link is intact or blown.

Since switching devices of this type are commonly opened for de-energizing a connected circuit so that workmen may safely contact the conductors of the disconnected circuit, the electrode 32 is preferably attached and movable with the fuse tube 34 as it is rotated to the disconnected position indicated by the dashed lines.

This construction assures the full use of the insulating strength of the insulator 25A as a protection for such workmen without destroying the protection oiered bythe device to excess voltages conducted to the line or energized terminal 30.

For certain applications, particularly those in which the exposure to atmospheric lightning disturbances of the load conductor `is much less than that of line conductor, it may be desirable to unbalance the spark gaps 31 and 38, so that the electrical strength of the former is substantially less than that of the latter. A preferred path is thus provided for the discharge to ground ot abnormal voltages arriving at the line end of the switch, which path does not include the fuse link, and this arrangement therefore prevents unnece'ssary fusing of the fuse' link under the conditions mentioned. To illustrate, in one desirable arrangement for a line operatingat a voltage of 13 kv., the gap 31 is 5/8" and the gap 38 is 1". In general, dependable selectivity cannot be obtained if the ratio of gap lengths exceeds about 0.65, which ratio applies to short gaps of the order mentioned.

It will be understood thatv the drawing and description herein are intended as illustrative rather than limiting, also that various modifications of our invention may be made without departing from' the principles of the invention, and our invention is to be limited only as is necessitated by the claims and the prior art.

We claim, as our invention: y

1. A switching device comprising insulating means supporting spaced terminals, movable conducting means for electrically connecting and disconnecting said terminals, and normally nonconducting excess-voltage means associated with said terminals, said excess-voltage means having terminals' at the respective ends thereof including a ground terminal and .being adapted to break downto effect ilow of current therethrough in respons'eto an abnormal predetermined voltage and to resume the normally non-conducting condition under normal voltage conditions, and structural means for providing preferential sparkover paths from each of said terminals to said ground terminal, each of said paths including said excess-voltage means.

2. A switching device comprising insulating means supporting spaced line and load terminals, conducting means movable to engage and disengage said terminals, and a single normally non-conducting excess-voltage means associated with said terminals, said excess-voltage means having a ground terminal and being adapted to break down to eilect current flow therethrough in response to a predetermined voltage and to resume the normally non-conducting state upon the restoration of normal voltage conditions, and structural means for causing sparkover from either of said terminals to said ground terminal to eiect ilow of current over a path of, which said excess-voltage means is a part. y

3. A switching device comprising insulating means supporting spaced terminals, conducting means movable to engage and disengagesaid terminals, a single normally non-conducting excessvoltage means associated with said terminals,

said excess-voltage means' having terminals at the respective ends thereof including a ground terminal and being constructed and arranged to break dovim to eii'ect ow of current therethrough in response to an abnormal predetermined voltage impressed between either of said spaced terminals and said ground terminal and to resume the normally non-conducting condition upon the re-establishment of normal voltage conditions, and structural means responsive to sparkover from either of said terminals to ground for eiecting current flow over one of two paths, and means electrically connecting said excess-voltage means in series circuit relation with each of said paths.

4. In a switching device', insulating means supporting spaced terminals, said insulating means including a normally non-conducting excessvoltage device adapted to breakdown to effect current flow therethrough in response to a predetermined voltage and to resume the normally non-conducting condition upon the restoration of normal voltage conditions, and structural means for causing current to iiow from either of said terminals through said excess-voltage device upon the occurrence of a predetermined abnormal and excessive voltage appearing upon either terminal.

5. In a switching device, insulating means supporting a line terminal and insulating means supporting a load terminal, spaced conducting electrodes constituting a spark gap arranged to bridge each of said insulating means, one of said electrodes of said spark gaps being common to both of said spark gaps, excess-voltage means having a ground terminal and a conducting terminal at the respective ends thereof, and means for electrically connecting said conducting terminal to the common electrode, said excess-voltage means being normally non-conducting and adapted to break down to effect ilow of current therethrough in response to the occurrence of an abnormal difference in potential between said common electrode and said ground terminal and to immediately resume the normal non-conducting condition upon the reoccurrence of normal difference of potential.

6. In a switching device, an excess-voltage responsive device, a conducting member, means for electrically connecting said excess-voltage responsive device between said conducting member and ground, insulating means supporting spaced line and load terminals, said insulating means being interposed between said conducting member and said line `and load terminals, and normally insulated conducting electrodes electrically connected to said line and load terminals respectively and extending toward said conducting member in spaced relationship therewith and arranged to provide the preferential spark paths from each of said terminals to said conducting member.

7. A switching device comprising a single excess-voltage responsive device, a. conducting member, means electrically connecting said excess-voltage responsive device between said conducting member and ground, insulating means supporting spaced line and load terminals, said insulating means being interposed between said conducting member and said line and load terminals, normally insulated conducting electrodes electrically connected to said line and load terminals respectively and extending toward said conducting member in spaced relationship therewith to provide preferential spark paths from each of said terminals to said conducting member, and movable conducting means for electrically connecting and disconnecting said terminals, one of said electrodes being fastened to and movable with said movable conducting means.

8. In a switching device, an excess-voltage responsive means, a conducting member, means electrically connecting said excess-voltage responsive means between said conducting member and ground, insulating means fastened to said conducting member and supporting spaced line and load terminals, said insulating means normally insulating said terminals with respect to said conducting member, a first conducting electrode electrically connected to the line terminal and a second conducting electrode electrically connected to the load terminal, said electrodes extending toward said conducting member in spaced relationship therewith and arranged to provide a spark gap between each electrode and said conducting member, the distance between said iirst conducting electrode and said conducting member differing with respect to the distance between said second conducting electrode and said conducting member.

9. A fused switching device comprising insulating means supporting spaced terminals, a fuse tube spanning said terminals and means including a fusible element within said fuse tube electrically connecting said terminals, a normally non-conducting excess-voltage means having terminals at the respective ends thereof including a ground terminal and being adapted to break down to effect ilow of current therethrough in response to an abnormal predetermined voltage and to resume the normally non-conducting condition under normal voltage conditions, and structural means for providing, when said fusible element is fused, a preferential sparkover path from each of said spaced terminals to said ground terminal, said path including said excess-voltage means.

10. A fused switchig device comprising a single excess-voltage responsive means, a conducting member, means electrically connecting said excess-voltage responsive means between said conducting member and ground, insulating means fastened to said conducting member and supporting spaced line and load terminals, said insulating means normally insulating said terminals with respect to said conducting member, a fuse tube spanning said terminals and means including a fuse link Within said tube normally electrically connecting said terminals, iirst and second conducting electrodes electrically connected to the line and load terminals respectively, said electrodes extending toward said conducting member in spaced relationship therewith and arranged to provide a spark gap between each electrode and said conducting member, the distance between said rst conducting electrode and said conducting member being less than the distance between said second conducting electrode and said conducting member, the arrangement being such that a predetermined voltage impressed initially o'n said line terminal effects ow of current from said line terminal to ground without aiecting ow of current through said iuse link.

11. A surge-protected fused switch comprising a single excess-voltage responsive and arc-extinguishing device, a conducting member, means electrically connecting said excess-voltage device between said conducting member and ground, in-

sulating means fastened to said conducting memberand supporting spaced line and load terminals, said insulating means normally insuating said terminals with respect to said conducting member, a swingably movable fuse tube spanning said terminals and means including a fuse link within said tube electrically connecting said teryminals, a first conducting electrode secured to said line terminal and a second conducting electrode fastened to saidfusetube and electrically connected to said load terminal, said electrodes extending toward said conducting member in spaced. relationship therewith and arranged to provide a spark gap'between each electrode and said conducting member, the arrangement being such thatl either of said spark gaps provides a l between said conducting member and ground, in-

sulating means fastened to said conducting member and supporting spaced line and load terminals, said insulating means normally insulating said terminals with respect to said conducting member, a removably mounted fuse tube spanning said terminals and means including a fuse link Within said tube electrically connecting said terminals, a first conducting electrode secured to l said line terminal and a secondconducting electrode secured to said fuse tube adjacent said load l terminal and electrically connected thereto, said electrodes extending toward said conducting member in spaced y relationship therewith and arranged to provide preferential spark gaps between each electrode and said conducting member, the distance between said rst conducting electrode and said conducting member differing from that between said second conducting electrode and said conducting member.

RALPH R. PrI'rMAN. CARROLL H. WALSH. 

